Method and system for storm water system heat exchange

ABSTRACT

A system and method for structure heating, ventilation, and air conditioning (HVAC) that uses a heat exchanger to transfer heat between the structure and a subsurface storm water discharge chamber system is disclosed. Coils for heat management exchange are located in permanently collected runoff within a storm water management system beneath the frost line; the use of coils located within the retained runoff allows for improved heat exchange over coils placed within soil. Also described are a sensing device and feedback loop for HVAC control, to improve efficiency at ambient temperatures near the subsurface temperature.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional application of U.S. patent applicationSer. No. 09/352,761, filed on Jul. 14, 1999, now U.S. Patent No.6,412,550B1, and claims priority to provisional application, Ser. No.60/108,890, filed Nov. 17, 1998, both incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to use of a storm water system for heatexchange and more particularly to a method and system for using anunderground storm water system for heat exchange for building heating,ventilation, and air conditioning (HVAC).

BACKGROUND

Many buildings and other structures for which heating or cooling isneeded provide temperature control using a closed loop system having aheat exchanger. A heat exchanger requires for operation a source foradding or removing heat from the structure. A common source for addingor removing heat that is known in the art involves capture of geothermalenergy, which is the energy from the earth or temperature from theearth, using a heat exchanger.

The operation of a heat exchanger can be understood by reference to theradiator of a car, which is one form of heat exchanger. In a car, heatfrom the engine is transferred to coolant circulated within the engine.The coolant is then pumped into a radiator, where heat is transferred tothe surrounding air, and the cooled coolant is returned to the engine tobegin the cycle again. In this manner, heat is transferred from theengine so as to maintain the temperature of the engine below the boilingpoint.

A similar approach is used to cool a structure, such as a building. Aheat exchanger connected to a building takes advantage of thetemperature difference between the ambient or surface air temperatureand a constant temperature source, such as relatively constantsubsurface temperature (subsurface temperature, as used herein, refersto the temperature at a depth of several feet below the surface of theearth, the depth of which depends on the climate and other conditions ofthe area; below this set depth, the temperature is known to generallyremain constant). The heat exchanger is used to transfer the temperaturedifference from the subsurface area to the building located on thesurface. Because the subsurface temperature is typically above thesurface temperature in Winter, heat may be transferred to the structurevia the heat exchanger to heat the structure, and because the subsurfacetemperature is typically less than the surface temperature during theSummer, the heat exchanger can transfer the heat in the building fromthe surface to the subsurface to cool the structure.

The relatively constant subsurface temperature of the earth is commonlyconsidered when laying water pipes or sewer pipes, as well as whenbuilding a structure. In these cases, it is often important that thepipes or structure be located below the frost line—the area within theground below which water freezes. Ground below the frost line has atypically somewhat higher temperature than the ambient air temperatureat the surface in Winter, and typically somewhat lower temperature thanthe ambient air temperature at the surface in Summer.

It is known in the art to provide this heat exchange by digging anexcavation, referred to as a field, for the structure, planting a closedloop heat exchanger in the earth for capturing or releasing heat. Aproblem with this approach is that the heat transfer coefficient betweenthe coolant contained in the closed loop of the heat exchanger and thesolid of the soil in which the loop is located is substantially lessthan the heat transfer coefficient for liquid-to-liquid or liquid to gasheat transfer. As a result, heat transfer using soil results ininefficiency compared to heat transfer using a liquid or gas.

For a completely unrelated reason to heat transfer, it is also known inthe art to provide subsurface storage of storm water for businesses andother developments, such as parking lots. These systems are referred toas underground storm water chamber systems. Subsurface storage caninclude storage tanks specially designed and constructed for thesefacilities, and storm water is also storable in above-ground constructs,such as surface ponds or impoundments.

Underground storm water chamber systems can be either detention systems,retention systems, or first flush attenuation systems. Detention systemsstore a calculated volume of storm water in the chamber. Water isreleased at a predetermined rate to an outflow structure. Retentionsystems also store a calculated volume of storm water in the chamber;however, the primary drainage mechanism in retention systems isinfiltration into the soil. First flush attenuation systems are similarto retention systems; however, they have limited capacity. Once capacityhas been met, excess storm water is released into an outlet. First flushattenuation systems are often used to take advantage of the soil'sfiltration and renovation capabilities when the inital runoff contains ahigh percentage of pollutants. The present invention can be used inconjunction with any form of underground storm water chamber system.

A storm water management system is designed for managing the dischargeof water from new construction so that the volume of water that leavesthe site is no greater that the volume before the construction began.For example, if the site was a meadow with trees and grass, typicalrunoff levels would be relatively small, such as ten percent of therainfall, with ninety per cent of the rainfall being absorbed into theground. After construction on such a site, however, runoff may be muchgreater than it was when the site was a meadow.

Whenever new construction occurs or there are other improvement toproperty, in general, a calculation must be made to ensure thatsufficient runoff storage capacity for the geographical area isprovided, such that the base line of rainfall that is anticipated in thearea from historical data is maintained. The calculations for storagecapacity are predicated on the historical rainfall information, so thatthe storage capacity of the storm water management system will have thecapacity to contain the predicted amount of runoff that can be expectedwith the new construction or other improvement, and this capacitymaintained and metered out at the same rate of discharge that wasoccurring before the construction.

This discharge from the storm water system typically is made to a stormdrain, which most municipalities and incorporated townships haveinstalled to keep water or storm water from collecting on the surface.In more rural areas, this discharge may typically occur onto neighboringproperty or into open swales or ditches along roadways. Municipalsystems that combine both sanitary and storm water systems typicallyfurther include backflow preventors installed from the storm watermanagement system, such that no sanitary effluent can back up into thesystem.

In order to accomplish the runoff collection and discharge needed, atypical storm water collection system collects runoff as quickly aspossible. For example, the system might include a thirty-six-inch pipeleading into the storm water management collection area to allow forsignificant inflow of runoff. The same system might also have only afour-inch diameter exit pipe to control the discharge. As a result,during a rainfall event, the system typically becomes inundated withrunoff, which is then discharged at a lower flow rate through the exitpipe. Thus, the net effect of collected rainfall on the property duringa rainfall event is that downstream receivers of the discharge receivethe same amount of water, which is metered out over time, as wasreceived prior to the new construction or other improvement.

Typical storm water management systems are further designed such that norunoff or only a small amount of runoff normally remains in the system.In these systems, the small amount of runoff typically remains in thesystem solely for water quality management purposes. These water qualitymanagement purposes, which are also unrelated to heat exchange, aregenerally mandated by the local water quality control authority,requiring that the quality of the water discharged from the storm watermanagement system be of the same quality as the rain water.

It is also known in the art to provide underground storage usingprefabricated units that are interlockable. An example of suchprefabricated units is the MAXIMIZER CHAMBER SYSTEM storm watertreatment device made by Infiltrator Systems Inc. of Old Saybrook, Conn.In this system, rows of individually prefabricated chambers areinterlocked to form a continuous storage space that is structurallytested to withstand high surface pressures, as from vehicles parkedabove the system.

Because underground storm water chamber systems are typically locatedbelow the frost line, any water within these systems will reach anequilibrium temperature regardless of the seasonal air temperature atthe surface above the system: For the same reasons as described above,this equilibrium temperature is typically below the surface airtemperature during Summer and above the surface air temperature duringWinter.

There is a need for a method and system for utilizing the intrinsic heatproperties of water stored in a storm water chamber system for operationin conjunction with conventional HVAC systems of structures, such asbuildings or other facilities, located near the storm water chambersystem to provide efficient heating and cooling of these structures.There is a further need to utilize a liquid-to-liquid or liquid-to-gasheat exchange for heating and cooling such facilities in conjunctionwith use of a storm water chamber system.

SUMMARY OF THE INVENTION

It is an advantage of the present invention to solve the problems of theprior art by utilizing existing excavation made for other purposes toprovide a location for a heat exchanger for a structure.

It is a further advantage of the present invention to provide a methodand system for utilizing the energy of water stored in a storm waterchamber system for operation with conventional HVAC systems of buildingsor other facilities located near the storm water chamber system to heatand cool these facilities.

It is a further advantage of the present invention to provide for a heatexchange system locatable within prefabricated storm water chamberchambers. It is a further advantage of the present invention to providefor an interlockable heat exchange system that is interlockable withunits of a storm water chamber system.

It is a further advantage of the present invention to provide for amethod and system for retaining a minimum volume of water within a stormwater chamber system having a heat exchange element, such that the heatexchange element remains immersed within retained runoff in the system.

It is a further advantage of the present invention to provide for amethod and system for feeding back information from the storm waterchamber system to the heat exchange portion of an HVAC system of abuilding or other facility to increase the efficiency of the system.

An embodiment of the present invention utilizes the excavation for astorm water management system to provide a source for capture ofgeothermal energy. This embodiment thereby uses a liquid-to-liquid orliquid-to-gas transfer ratio because the coil containing the liquid orgas medium of the heat exchanger is immersed in the liquid runoff thatis contained within the storm water management system.

An embodiment of the present invention includes a closed loop heatexchanger system having connections by, for example, pipes containing afluid or gas heat exchanger medium, and other components. The componentsof this embodiment include a pair of heat exchanger portions connectedby a loop, and a pump that serves as a circulator for the heat exchangemedium. In an embodiment of the present invention, the circulator movesthe medium between an above ground heat exchanger, such as a radiator,for example, located in a building, and a below ground heat exchangerthat includes coils located within a storm water chamber system. Anembodiment of the present invention further includes a sensing device,such as a thermocouple, and feedback loop for HVAC control, to improveefficiency at ambient temperatures near the subsurface temperature.

Additional objects, advantages and novel features of the invention willbe set forth in part in the description that follows, and in part willbecome more apparent to those skilled in the art upon examination of thefollowing or upon learning by practice of the invention.

BRIEF DESCRIPTION OF THE FIGURES

In the figures:

FIG. 1 depicts a perspective view of an example underground storm watersystem heat exchange and HVAC system according to an embodiment of thepresent invention;

FIG. 2 shows a closeup perspective view of the storm water system heatexchange component of an embodiment of the present invention;

FIGS. 3A and 3B present perspective views of two differentconfigurations of connected units of the storm water heat exchangecomponent of an embodiment of the present invention;

FIG. 4 presents a flow diagram of the storm water heat exchanger processof an embodiment of the present invention; and

FIG. 5 shows a closeup perspective view of one configuration of thestorm water heat exchange component of an embodiment of the presentinvention.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate an embodiment of the present invention thatincludes a closed loop heat exchanger system 1, 2 a, 2 b, 15 havingconnections by, for example pipes containing a fluid or gas heatexchanger medium, and other components. The components of thisembodiment include a pair of heat exchangers portions 3, 15 connected bya loop 2 a, 2 b, and a pump 3 that serves as a circulator for the heatexchange medium. In an embodiment of the present invention, thecirculator 3 moves the medium between an above ground heat exchanger 3,such as a radiator, for example, located in a building 4, and a belowground heat exchanger 15 that includes coils located within a stormwater chamber system 1. The storm water chamber system 1 maintains acontinuous level of contained runoff 11. An embodiment of the presentinvention further includes a storm water chamber system temperaturesensing device 26, a structure internal temperature sensing device 6,which may include, for example, a thermocouple, and feedback loop forHVAC control 5 to improve efficiency at ambient temperatures nearsubsurface temperature.

When the base is pourous, it is more difficult to maintain a continuouslevel of runoff between rains. FIG. 5 shows one embodiment of thepresent invention designed to capture runoff water 24 when the base isunable to sufficiently retain a proper water level. Retaining walls 23capture and hold runoff water 24 when the water level rises above theretaining walls 23. When the water level falls back down due to theporous base, the captured runoff water 24 can still be used to increasethe efficiency of heat transfer. To minimize evaporation, water retainertops 22 are used to cover the captured runoff water 24. This embodimentcan also be used as additional reservoirs for pollutants to collect.

As discussed above, typical existing unit-type storm water chambersystems are expandable and combinable. The units come in easilytransportable sections that are attachable together and may be assembledin the field, after excavation is completed. In accordance with anembodiment of the present invention, coil capacity for a heat exchangeris integrated into these units, such that the portions of the heatexchanger system may be similarly sectioned together.

In an embodiment of present invention, a coil, which is embedded intothe system, is molded into the units of the system when made, andcertain fittings that allow the flexibility to terminate and to createloop conditions are included, such that the system may be expanded tothe size needed for the storm water management system. For example, toincrease the size of the system, a combination of fittings is used thatallows the system to be made longer, shorter, or wider, in whateverconfiguration that is needed.

In another embodiment of the present invention, the coil is woventhroughout the bottom of the storm water chambers providing increasestructural integrity by resisting spreading at the bottom of the stormwater chambers when extreme pressures are applied such as that caused byan automobile parking above a storm water chamber. Additionally, thecoil must be configured to prevent crimping when extreme pressures areplaced on the tubing.

Two configurations of connected units according to this embodiment areshown in FIGS. 3A and 3B. In FIG. 3A, units 1 a, 1 b, 1 c are connectedlengthwise to provide a storm water management system heat exchangercomponent that has a rectangular shape, as viewed from overhead. In FIG.3B, the units 1 a, 1 b, 1 c, 1 d are arranged so as to form a generallyL-shaped storm water management system heat exchanger component, asviewed from overhead. Such a system can also include loops on the endsthat are orientable in a left-handed or right-handed direction, andultimately leadable to a location where a supply line and a return lineare attached.

In an embodiment of the present invention, rather than discharging fromthe bottom or the lowest point of the storm water management system, asis typical in the prior art, runoff is discharged at a predeterminedlevel, such that a permanent volume of runoff is maintained in thesystem. For example, an embodiment of the present invention may includesix feet of water permanently maintained in the bottom of the stormwater management system. In this embodiment, the coil of the heatexchanger is located at the bottom of the maintained water level, whichallows the achievement of a higher transfer rate from the subsurfaceportion of the heat exchanger system than would occur if the heatexchanger used soil for the heat transfer.

As shown in FIG. 1, the system of an embodiment of the present inventionincludes units 1 made of a plastic material that are premolded,joinable, and have sufficient strength to withstand vehicles and otherpressures from parking lots or other construction placed above thesystem. In a typical use of these units, they are connected to oneanother in a manner prescribed by the manufacturer such that the systemas a whole stores storm water in a fashion that is consistent with thelaws of the natural resources management authority, as described above.

In FIG. 1, a heat exchange system (shown in FIG. 2) within a storm watermanagement system 1, having an inlet 12 and a storm drain outlet 16, isconnected by a return line 2 a and a supply line 2 b to a heat exchangerand circulator unit 3 within a structure 4, such as a building. Thecirculator unit 3, which is located in the structure 4, operates inconjunction with the structure HVAC system 5.

In an embodiment of the present invention, runoff from the surface 10collects via the inlet 12 in the storm water management system 1. Thecollected runoff in turn is released from the storm water managementsystem 1 to the storm drain 14, by, for example, reaching a level 11above the height of the storm drain outlet 16 for the storm drain 14. Inan embodiment of the present invention, a predetermined volume of liquidform the collected runoff remains within the storm water managementsystem at this level 11.

FIG. 2 shows a closeup view of the subsurface storm water system heatexchange component of an embodiment of the present invention. In FIG. 2,the permanent water level 11 is presented on the scale located on theright hand side of the figure, and the dotted line depicts the permanentwater level 11 within the system 1 for an embodiment of the presentinvention. Also shown is the loop of the heat exchanger 15, which islocated below the permanent water line 11 retained within the system 1.

As shown in FIG. 2, an embodiment of the present invention furtherincludes a storm water chamber system temperature sensing device 26located within the storm water management loop that feeds informationback to the energy management system in the building or other structure,such that optimal or otherwise more beneficial times for operating thecirculator for the heat exchanger may be determined.

For example, at certain times, it may be determined that the ambient airtemperature is close to the temperature that is to be maintained insidethe structure. In this situation, the cost to circulate the circulatorcould exceed the benefits of the relatively small fraction oftemperature difference between the retained water and the surfaceambient temperature. The storm water chamber system temperature sensingdevice 26 is employed to feed back monitoring information to any energymanagement portion of the system so that the system only attempts tocapture energy when it was suitable to do so.

FIG. 4 presents a flow diagram of the heating and cooling operation ofthe heat exchange system in accordance with an embodiment of the presentinvention. As shown in FIG. 4, in step S1, a structure internaltemperature input is received. In step S2, a retained storm watertemperature input is received. In step S3, a selection of heating orcooling is made. In step S4, a temperature comparison is made betweenthe structure internal temperature input and the retained storm watertemperature input.

In step S5, it is determined whether a selection for heating or coolinghas been made. If heating is selected in step S5, the system proceeds tostep S6. In step S6, a determination is made as to whether the internaltemperature is less than the retained storm water temperature. If no instep S6, the system returns to step S4 for temperature comparison. Ifyes in step S6, heat is transferred from the storm water system heatexchanger to the structure heat exchanger, so that the structure isheated.

In step S5, if cooling is selected, the system proceeds to step S8. Instep S8, a determination is made as to whether the internal temperatureis greater than the retained storm water temperature. If no in step S8,the system returns to step S4 for temperature comparison. If yes in stepS8, heat is transferred from the structure heat exchanger to the stormwater system heat exchanger, so that the structure is cooled.

In one embodiment of the present invention, in step S3, a selection ofheating or cooling is made based on the outdoor air temperature. If theoutdoor air temperature is cooler than the internal temperature andcooling is desired, it is unnecessary to activate the primary coolingsystem. Conversely, if the outdoor air temperature is warmer than theinternal temperature and heating is desired, it is unnecessary to activethe primary heating system.

Embodiments of the present invention have now been described infulfillment of the above objects. It will be appreciated that theseexamples are merely illustrative of the invention. Many variations andmodifications will be apparent to those skilled in the art.

1. A method for providing heat conduction for a structure using a stormwater management system located below a frost line, the structure havinga structure internal temperature, the storm water management system isprefabricated to contain a first heat exchanger and retain a liquidrun-off, wherein the first heat exchanger is immersed in the liquidrun-off, the liquid run-off having a liquid run-off temperature; aconnecting line connected to the first heat exchanger; and a second heatexchanger connected to the connecting line, the second heat exchangerconducting heat directly with the structure, the method comprising:determining the structure internal temperature; determining the outdoorair temperature; determining the liquid run-off temperature; making aselection from the group consisting of heating and cooling, wherein theselection is substantially based on the outdoor air temperature;comparing the liquid run-off temperature to the structure internaltemperature; and determining whether to transfer heat between the secondheat exchanger and the first heat exchanger that is contained in theprefabricated storm water management system.
 2. The method of claim 1,further comprising: if the liquid run-off temperature is less than thestructure internal temperature and the selection is cooling,transferring heat from the second heat exchanger to the first heatexchanger.
 3. The method of claim 1, further comprising: if the liquidrun-off temperature is greater than the structure internal temperatureand the selection is heating, transferring heat from the first heatexchanger to the second heat exchanger.
 4. The method of claim 1,wherein the storm water management system further comprises a stormwater chamber system temperature sensing device, and wherein determiningthe liquid run-off temperature comprises receiving data from the stormwater chamber system temperature sensing device.
 5. The method of claim4, wherein the storm water chamber system temperature sensing devicecomprises a thermocouple.
 6. The method of claim 1, wherein thestructure further comprises a structure internal temperature sensingdevice, and wherein determining the structure internal temperaturecomprises receiving data form the structure internal temperature sensingdevice.
 7. The method of claim 1, wherein the selection is received froma user.
 8. The method of claim 1, wherein the first heat exchangerprovides increased structural integrity to the prefabricated storm watermanagement system.
 9. A method for providing heat conduction for astructure using a storm water management system located below a frostline, the storm water management system containing a first heatexchanger and retaining a liquid run-off, wherein the first heatexchanger is immersed in the liquid run-off, the liquid run-off having aliquid run-off temperature; a connecting line connected to the firstheat exchanger; and a second heat exchanger connected to the connectingline, the second heat exchanger conducting heat directly with thestructure, the method comprising: determining the outdoor airtemperature; making a selection from the group consisting of heating andcooling, wherein the selection is substantially based on the outdoor airtemperature; if the selection is heating, transferring heat from thefirst heat exchanger to the second heat exchanger, such that thestructure is heated; and if the selection is cooling, transferring heatfrom the second heat exchanger to the first heat exchanger, such thatthe structure is cooled.